Method and apparatus for producing decorative effects by spotting or mottling



Sept. 29, 1931. R. F. GRADY, JR 1,825,227

METHOD AND APPQRATUS FOR PRODUCING DECORATIVE EFFECTS B Y SPOTTING OR MOTTLING' Filed Sept. 26. 1929 H ALATTORNEY Patented Sept. 29, 1931 PATENT OFFICE ROBERT FRANKLIN GRADY,

IR, OF CHICAGO, ILLINOIS METHOD AND APPARATUS FOR PRODUCING DECORATIVE EFFECTS BY SPOTTING OB MOTTLING Application filed September 26, 1929. Serial No. 395,244.

This invention relates to the production of decorative efi'ects by means of spotting or mottling, particularly to the application of slips and glazes on terra cotta and other ceramic ware to produce speckled, spotted or mottled ell'ects.

Practically all architectural terra cotta made to-day has a body of butt-burn ng clay; all decorative effects in color being produced by means of slips or glazes applied by means of sprays or air brushes. Where solid colors are called for the technique of application is relatively simple. Given a uniform supply of coating material fed under a constant head, a skilled operator experiences no great difficulty in applying a uniform coat of glaze or slip to the surface of the clay. But where speckled, spotted or mottled effects are required, as sometimes in the imitation of granites and other varicolored building stones, the production of satisfactory results is more difficult. 4

Various methods have been employed in producing these spotted effects and numerous machines have been designed, but none has been found wholly satisfactory over the wide range of effects required. In accordance with the present invention I have provided an improved method for producing these spotted effects and an improved machine for carrying it out, the machine being simple in construction, admitting of easy control, and capable of producing spots varying in size from more specks tov splotehes two and one half inches in diameter. In practicing my invention I utilize a source of pulsating air pressure by meansof which predetermined amounts of the" color are flung upon the ware in a series of intermittent spurts. The size and number of the resultant spots can be controlled by regulating the amount of color, the size of the discharge outlet, and pressure and frequency of the air impulses. The greater the air pressure and the smaller the outlet, the smaller the spots with a given feed.

' In pract-ice I have successfully employed a valveless air motor as ''the source of my pulsating air pressure, the alternate exhausts from such a motor serving admirably for this purpose. Two nozzles are employed,

each exhaust port being connected to one nozzle. By utilizing a separate supply of color for each nozzle,-spots of two difi'erent colors can be applied simultaneously, and if a greater number are desired the be split.

In the accompanying drawings in which I have illustrated a preferred embodiment of my invention Figure l is a sideelevation of a spotting machine construction in accordance with the present invention; Figure 2 is a plan view of this construction; Figure 3 is a transverse section taken along line 33 through the air motor and one of the nozzles; Figure 4 is a transverse section taken along line 4-4 of Figure 1 and illustrating a trigger whereby the flow of slip or glaze can be manually controlled; and Figure 5 is a horizontal section through the air motor along line 5-5 of Figure 1.

The spotting machine illustrated in these drawings comprises a bottom plate 1 having a long, straight shank and an end portion turned at an angle of 135. On this end portion is mounted a valveless air motor 2' having superposed thereon 'a pair of nozzles 3 to which glaze or slip is supplied through a pair of rubber tubes 4 extending along the platel. Compressed air for the nozzles is delivered from the exhaust ports of the motor. The motor is supplied with air through a pipe 5 extending along the plate 1 and above the tubes 4. And now after this very general description ofthe construction of the machine I shall describe it in greater detail, referring first to Figure 3.

Each delivery nozzle 3 comprises a barrel portion 6 terminating at its forward end in a removable tip 7 and at its rearward end in an elbow 8 which serves as a glaze inlet to which a tube 4 is connected. The barrel 6 thus provides a chamber in front of the air nozzle'where the liquid can collect between impulses of air. Compressed air is fed to the nozzle through an air inlet tube 4) which enters the rear wall of the elbow 8 and extends inward coaxially with the barrel 6, forming an ejector. Compressed air for this ejector passes through exhausts can a pipe 11 from one of the exhaust ports 15, of the air motor 2. I shall now describe this air motor with particular reference to Figure 5.

The motor which I have successfully used is a simple valveless air motor of the t pe extensively used in air drills, and whlch, of itself, forms no part of the resent invention. I shall, however, brie describe its construction and operation. he motor comprises a cylinder 13 to which compressed air is fed through an inlet port 14, and from which it is discharged through exhaust ports 15, 15. Mounted within the cylinder are a air of pistons 16, 16 connected by means of a shank 17 of less diameter. pposite the inlet and exhaust ports the cylinder is provided with by-passes 18, 18' communicating with the cylinder through inner ports 19, 19 and outer ports 20, 2 The motor operates as follows: Starting from the position illustrated, air entering through the port 14 passes through port 19, by-pass 18', port 20, and into the cylinder on the far side of the piston 16. As the area of the end face of the piston is reater than the annular area of its inner ace, the air pressure in the end of the cylinder moves the pistons toward the left. This movement covers port 19 and uncovers exhaust port 15 through which a puff of air spurts. At the same time piston 16 uncovers port 19 and the operation is repeated in the lefthand end of the cylinder. Thus, as long as compressed air is fed to the motor, the pistons 16, 16 reciprocate within the cylmder and air is alternately exhausted from the two ports 15, 15, producing a pulsating pressure in each. The number of reciprocations per unit time for the pistons 16, 16' is a factor of the air pressure so that the frequency of the air pulsations created in the exhaust orts can be controlled by a regulation of this pressure. Each of these exhaust ports is connected through a pipe 11 to the e ector of one of the nozzles so that as lon as the motor is running each nozzle is sub ected to a pulsating pressure. The motor acts, in effect, as an automatic valve opening and closing to interrupt the flow of air in pipe 5 and produce pulsations.

Each pipe 11 is provided with a ball check valve 22 so designed that although air can pass freely from the motor to the nozzles no slip or glaze can inadvertently back up through the tubes 11 and enter the motor.

The flow of slip or glaze through tubes 4 is preferabl regulated by varying the head under whic it moves. This flow can also be controlled manually if desired by means of a cut-off mounted upon the plate 1. This cut-oif comprises a sharp-edged cross-bar or yoke 23 extending across the plate 1 beneath the air pipe 5 and above the glaze tubes 4 and connected by means of a stem 24 to 9.

s ring steel trig er 25, one end of which is fixed to the under side of the plate 1, as illustrated. This trigger 25 normally moves outward to press the sharp edge of the cross-bar 23 against the tubes 4 to close them and prevent the flow of color so that during the operation of the device, it is necessary for the operator to com ress the trigger spring with his hand and t us hold the cross member 23 of the cut-off against the pipe 5 and out of closing contact with the tubes. These tubes are illustrated in Figures 1 and 4 in the normally closed position. In order that the operator may obtain a firm ip upon the device which would enable im to compressthe spring 25 with a minimum of effort, I have provided an arcuate guard plate 26 secured at one end to an end plate 27 mounted on the bottom plate 21, the guard plate extending along the upper side of the pipe 5.

In operation the motor is connected, through tube 5, to a suitable source of compressed air which reciprocates the pistons and establishes a pulsating air current at the two motor exhausts. Shp or glaze is fed continuously to the nozzles through the tubes 4, and entering the barrels 6 isintermittently ejected through the tips 7 by the pulsating air entering through the ejector. Although the slip or glaze itself is free flowing it does not emerge from the nozzle in a continuous stream or spray because the air impulses eject it in' intermittent discharges as slugs or gobs moving at greater speed than the speed of flow through the tube 4. In the intervals between impulses the slip or glaze for the next discharge gathers in the nozzle. The amount of liquid color which is ejected with each pulsation depends upon the amount of color fed to the nozzles which, in turn, depends upon the rate of flow and the frequency of the pulsations. With a low air pressure and consequent low frequency pulsations more color can accumulate in the nozzles between impulses, hence, with a given feed, the spots will be larger and greater fre uency are employed. The size of the tips also is a factor in determining the character of the spotting. Other things being equal, the smaller the outlet orifice the smaller the spots. By employing two different glazes or slips I can produce variegated color effects in one spotting operation. If more than two colors were desired! each exhaust from the motor could be caused to. feed a plurality of tubes 11 each of which would lead the air to a differentnozzle. I can also, of course, produce spots of difi'erent sizes at the same time by employing a small tip in one nozzle and a large tip in the companion nozzle. Thus without going into an exhaustive discussion of operative detail suflicient has been said to inthan when a higher pressuredicate that by intelligent control of rate of feed, air pressure and outlet size any desired effect can be produced.

' The machine described can be made extremely light weighin in all from two and one half to three poun s. Spottin machines previously employed have weig ed from eleven to thirteen pounds. My machine is simple in operation, and, having but one moving part which does not come in contact with the glaze or slip and can be replaced in two minutes, is not likely It is capable of a nice regulation and can produce spots blotches two and one half inches in diameter. Unlike other spotting machines it does not cause separation of the slip and glaze components when low air pressures are used and the spots which it produces at low pressures are not round and smooth like rain drops but have the desired irregularity of pattern. Hence the machine is equally satisfactory when making either big or little spots.

I claim:

1. Apparatus for producing spotted or mottled efiects which comprises a valveless air motor having two exhausts, means for conveying air under ressure to the motor whereby pulsations o the exhausts in alternation, two nozzles, a connection between each exhaust and one of the nozzles, two sources of liquid color, and means for conveying one color to each nozzle whereby spurts of color are intermittently and in alternation ejected from the nozzles.

2. Apparatus for spotting terra cotta which comprises two nozzles, ejectors communicating with said nozzles, a valveless air motor having two exhaust ports, a connection between each exhaust port and one of the ejectors, two sources of colored slips or glazes, tubes conveying the slips or glazes to the nozzles and means for conveying air under pressure to the motor thus roducing alternating pulsations of air in t e ejector tubes and intermittently throwing spots of colored slip or glaze from the nozzles.

3. In the apparatus as claimed in claim 2, means for controlling the flow of slip or glaze to the nozzles, and check valves in the connections between the exhaust ports and the ejectors preventing back flow of the slip or glaze into the motor.

In testimony whereof I aflix m si ROBERT FRANKLIN GR D ature.

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